The present invention relates to the field of mass storage devices. More particularly, this invention relates to a slider having an air bearing surface with high wear material pads and to the method for manufacturing the same.
One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are an information storage disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc.
The transducer is typically placed on a small ceramic block, also referred to as a slider, that is aerodynamically designed so that it flies over the disc. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface (xe2x80x9cABSxe2x80x9d) which includes rails and a cavity between the rails. When the disc rotates, air is dragged between the rails and the disc surface causing pressure, which forces the head away from the disc. At the same time, the air rushing past the cavity or depression in the air bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring which produces a force on the slider directed toward the disc surface. The various forces equilibrate so the slider flies over the surface of the disc at a particular desired fly height. The fly height is the distance between the disc surface and the transducing head, which is typically the thickness of the air lubrication film. This film eliminates the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation. In some disc drives, the slider passes through a layer of lubricant rather than flying over the surface of the disc.
Information representative of data is stored on the surface of the storage disc. Disc drive systems read and write information stored on tracks on storage discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the storage disc, read and write information on the storage discs when the transducers are accurately positioned over one of the designated tracks on the surface of the storage disc. The transducer is also said to be moved to a target track. As the storage disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the storage disc. Similarly, reading data on a storage disc is accomplished by positioning the read/write head above a target track and reading the stored material on the storage disc. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track.
Generally, disc drives shut down in two ways. In the first type of disc drive, the actuator offloads a portion of an actuator arm to a ramp which in turn prevents the slider from contacting the disc when it stops. This type of disc drive is a ramp load/unload disc drive. The other type of disc drive is a contact start and stop (xe2x80x9cCSSxe2x80x9d) disc drive. In a CSS disc drive, when the disc drive becomes nonoperational, the slider comes to rest on the disc surface, typically on a landing zone arranged at the inner or outer diameter of the disc, away from data tracks. At the onset of drive operation, the spindle motor has to provide enough power to overcome the static friction between the slider and the disc surface (also known as stiction in the magnetic recording industry). After the disc is rotated to the full operational speed, the slider is separated from the disc surface and flies above the disc surface to read or write information on data tracks. The contact start/stop functionality is often evaluated using a contact start/stop testing method in which the drive is operated to go through repeated starting and stopping modes for many cycles with a measurement of stiction at each CSS cycle.
The fly height between the discs and the sliders and included transducing heads during operation of the disc drive, has been reduced significantly during the last few years to achieve a higher recording density. Accordingly, it has been found to be necessary to form the disc surface to a very smooth finish to assure little or no head/disc contact during fly height operation of the disc drive. However, a smooth disc surface induces high stiction, especially with the existence of a liquid at the head/disc interface. Therefore, it is a common practice in the magnetic recording industry to roughen or texture the disc surface to reduce stiction during contact start and stop operations of the disc drive. Optimization of surface texturing has become a critical technology in disc drive manufacturing.
A further technology trend is to use a zone textured disc. In a zone textured disc, the landing zone (where the slider is resting when the drive is off) is textured by laser or other mechanical means. However, the data zone (containing the data tracks where the head is reading or writing information at a fly height) is either not textured or slightly textured to reduce the head/disc contact during the drive operation. This technique enables separate. optimization of each of the CSS landing zone and the data zone, to achieve lower head/disc spacing for a higher recording density, while reducing stiction encountered during contact stops and starts. When the zone textured discs are used in the drive, however, some special procedures have to be adopted during drive assembly to avoid a head from coming into contact with the disc surface within the data zone. Also, the actuator has to provide enough latch force to prevent the head from contacting the disc surface within the data zone during shipping and after the drive is turned off. If such contacts occur, the high stiction at the head/disc interface within the smooth data zone will prevent the drive from starting. In some cases, attempting to start the disc drive results in removing the slider from the actuator arm of the disc drive.
As magnetoresistive (MR) heads are introduced into disc drives, a layer of carbon overcoat is often applied to the slider surface to protect corrosion of read element and the write element. One of the side benefits of a carbon overcoat on the slider surface is that the stiction at the head/disc interface is also reduced significantly. The major drawback of a carbon overcoat, however, is that the effective head/disc spacing is also increased by an amount equal to the thickness of the carbon overcoat. Thus, there is a compromise between the head/disc magnetic spacing requirement and the stiction requirement for an optimal head/disc interface design.
In order to achieve ever higher magnetic recording density, a very smooth disc surface has to be used and the thickness of the carbon overcoat on the slider surface has to be reduced to a minimum amount. Two important issues have to be resolved to achieve the above objectives: lower stiction at the head/disc interface when a smooth disc is used and protection of the read/write elements against environmental corrosion when an MR head is used.
One solution proposed in the prior art is described in xe2x80x9cStiction Free Slider for the Smooth Surface Discxe2x80x9d (IEEE Transactions On Magnetics, Vol. 31, No. Nov. 6, 1995). The IEEE article illustrates a slider having three separated and isolated cylindrical carbon overcoat pads. One of the pads is formed at the center of one end of the slider, and the other two pads are formed at the other end of the slider, spaced from one another, with each pad being proximate to one of the side edges of the slider. The IEEE article states that the three isolated pads reduce stiction at head/disc interface when a smooth surface disc is used in the disc drive. However, the three, isolated pad arrangement described in the IEEE article has several drawbacks.
First the effectiveness of the pads depends on the profile orientation (crown, camber and twist) of the slider. For a wide range of slider profiles, which are typically encountered in a practical manufacturing environment, parts of the slider other than the pad locations, may be in contact with the disc surface. In that case the stiction at the head/disc interface will be very high. Secondly, there is no back-up support for the head/disc interface once one of the pads is worn away or becomes defective. Finally, for a laser zone textured disc, the disc surface has a discrete surface texture, and the use of a few spaced and isolated pads will not result in head/disc contact only at a pad location of the slider.
Another solution has been to provide a number of carbon overcoat pads or protrusions. A carbon overcoat is applied to the ABS surface in an array of individual carbon overcoat protrusions that are spaced across the slider surface and comprise a small and discrete area of the ABS surface. This technology is referred to as SLIP (slider integrated pads). Generally, the carbon overcoat protrusions comprise a total surface area equal to approximately 1% to approximately 15% of the total surface area of the slider. Each carbon overcoat protrusion is of a thickness sufficient to assure that head/disc contact only occurs where there is one or more carbon overcoat protrusions, but thin enough to have little effect on the flying characteristics of the slider. Using SLIP, the contact area of the head/disc interface is limited to the 1% to 15% total area provided by the array of carbon overcoat protrusions to reduce stiction at head/disc interface.
The use of carbon overcoat type slider integrated pads has several disadvantages. Among the disadvantages are that the slider integrated pads made of carbon, such as diamond like carbon wear over time or over the life of the disc drive. The root cause of stiction is the backward tipping of the slider or head. Excessive pad wear exacerbates the problem of backward tipping. In addition, the gap between the transducer housed in the slider and the disc changes during the life of the disc drive. Currently, discs may be provided with a relatively hard carbon overcoat that may be harder than the slider integrated pads. This may lead to excessive pad wear and to backward tipping and stiction.
In the current SLIP design, the pads are made of diamond-like carbon (DLC) by means of ion beam deposition. With a typical hardness of 25 GPa, the DLC pads are indeed harder than carbon overcoat on media, whose hardness ranges from around 10 GPa for sputtered carbon and around 14 GPa for ion beam carbon. However, as the total pad area for a SLIP head is less than 10,000 xcexcm2, it always represents a challenge to design a disc, with or without shallow LZT, that will meet the goal of limiting pad wear to below 50 xc3x85 after repeated contact start-stop operations. For media coated with ion beam carbon, which is superior to sputtered carbon in preventing corrosion problems, pad wear is particularly severe, in part due to its DLC-like hardness. Higher media overcoat hardness leads to substantially accelerated pad wear in contact start-stop testing.
The hardness of carbon can be controlled in some processes. In ion beam deposition, the harder carbon is formed by increasing the bias voltage during the process of ion beam deposition. In other words, the higher the bias voltage, the greater the hardness of the slider integrated pads formed. Making pads of harder carbon is not the solution, however, since pads of harder carbon wear more than pads of less hard carbon. For example, slider integrated pads formed at approximately 120 volts of bias voltage wear more than 200 angstroms after approximately 10,000 start stop cycles. In contrast, slider integrated pads formed at approximately 0 volts of bias voltage wear more than about 50 angstroms after approximately 10,000 start stop cycles. Therefore, merely making the slider integrated pads of harder carbon is not a solution since the slider integrated pads of harder carbon tend to wear more than the other carbon slider integrated pads.
What is needed is a slider having an air bearing surface that includes slider integrated pads that prevent the slider from backward tipping as the slider integrated pads wear over time. What is also needed is a slider having slider integrated pads that prevent stiction problems. Still further, what is needed is a slider that has a more consistent gap distance between the magnetic transducer and the disc over the life of the disc drive.
A disc drive includes a base and a disc rotatably attached to the base. The disc includes an overcoat material on the disc. The overcoat material has a first hardness. The disc drive also includes an actuator having a slider with an air bearing surface. The air bearing surface is provided with at least one slider integrated pad having a second hardness that is greater than the first hardness. In one embodiment, the at least one slider integrated pad is formed from SiC. The slider further includes a leading edge and a trailing edge. The at least one slider integrated pad is located near the trailing edge of the slider. There also may be at least one group of slider integrated pads formed from SiC. A first group of slider integrated pads is formed from SiC, and a second group of slider integrated pads is formed from diamond like carbon. The first group of slider integrated pads is located near the trailing edge of the slider. The at least one slider integrated pad is formed from SiC and the overcoat on the disc is formulated of carbon sputtered onto the surface of the disc. The overcoat may also be formulated of carbon deposited onto the surface of the disc in the presence of a bias voltage.
A slider for a disc drive is adapted to interface with an interface surface having a specific hardness. The slider includes a leading edge, a trailing edge, an air bearing surface positioned between the leading edge and the trailing edge of the slider. In addition, a plurality of slider integrated pads are positioned on the air bearing surface and at least some of the slider integrated pads having a hardness which is greater than the hardness of the interface surface. The slider integrated pads having a hardness which is greater than the hardness of the interface surface are located proximate the trailing edge of the slider. These slider integrated pads located proximate the trailing edge of the slider wear less than less hard slider integrated pads. The slider integrated pads have a hardness which is greater than the hardness of the interface surface. The slider integrated pads are formed of SiC.
In addition, a method of forming a slider having a leading edge, a trailing edge, and an air bearing surface includes the steps of forming a first set of slider integrated pads having a first hardness, and forming a second set of slider integrated pads having a second hardness different than the first. The harder slider integrated pads of the first or second set of slider integrated pads are formed near the trailing edge of the slider. The forming step further includes providing a mask which includes an array of openings for forming the first set of slider integrated pads, and depositing a material onto the mask and through the openings in the mask to form the first set of slider integrated pads. The forming step also includes providing a mask which includes an array of openings for forming the second set of slider integrated pads. The mask covers the first slider integrated pads. A material is then deposited onto the mask and through the openings in the mask to form the second set of slider integrated pads.
Advantageously, a slider having an air bearing surface that includes slider integrated pads made of SiC prevents the slider from backward tipping as the slider integrated pads wear over time. Thus the slider integrated pads made of SiC help to prevent stiction problems. In addition, the slider that includes slider integrated pads made of SiC has a more consistent gap distance between the magnetic transducer and the disc over the life of the disc drive.